The present disclosure is directed to an insert for use in bearings drill bits, or other high wear applications and more particularly to an insert which is formed of hard metal and which is also provided with diamond or PDC hard surface material. PDC material is an industrial type diamond which is manufactured to a particular size and shape. It can be shaped so that it provides protection to the insert. The insert protected with the PDC cladding is able to last much longer. The insert is thus a composite made of a hard metal with the diamond or PDC which is cast to it or brazed in place. As will be understood, the two components which makeup such an insert do not easily go together. Rather, these are manufacturing processes which are somewhat difficult to carry out. This inevitably results from the fact that the finished product is an extremely hard composite insert which is very rugged and able to withstand tremendous levels of abrasion, shock and impact.
In drilling an oil well the drill bit is normally used to advance the well borehole by drilling into formations of rock of any degree of hardness that is encountered. In an extremely hard formation, the rate of wear on the drill bit is substantial. It is appropriate to protect the drill bit by incorporating very hard inserts. These serve as teeth in the fabricated drill bit. The fabricated drill bit incorporates these teeth for the express purpose of drilling through extremely hard materials. Such inserts are subject to extreme levels of wear compared to the remainder of the body of the drill bit, and for this reason, the drill bit is constructed with such inserts. In the fabrication of an individual insert, a body portion is normally formed of very hard metal. It is then clad with diamond or PDC material. This is attached by various bonding techniques, the most common being brazing. This approach in fabrication is highly desirable but it is difficult to execute in most instances. In one aspect of the present invention, a manufactured insert is set forth which is particularly able to withstand stress of usage for longer intervals than heretofore accomplished. The enhanced insert has much longer life. Partly, that results from the improved manufacturing process which will be described in some detail below.
Consider an insert which is exposed to wear on all sides of the insert. This typically occurs to inserts at certain locations on a rotary drill bit. The different sides of the insert are exposed at different points in the rotation of the drill bit to abrasive wear from hard formation materials. The present disclosure sets forth a cylindrical insert which is formed of hard metal and which has lengthwise strip of diamond or PDC material on the outer cylindrical face. In one embodiment, the strips extend lengthwise and parallel to the cylindrical shape of the insert body. In another embodiment, the lengthwise strips are set at an angle so that they form a part or an entire helical turn. The helical turn is provided with a sufficient lead angle that one or more helical inserts provides protection to the external face of the cylindrical insert.
In another aspect of the present invention, the upper end or exposed face at the tip of the insert is likewise protected. This tip is constructed with a crown or covering. The crown or covering comprises a diamond or PDC layer which is joined to the device. In particular, there is a problem in manufacturing so that the insert during fabrication serves as a support on which the crown is cast. In the region around the edge of the face where the cylindrical body starts, there is some difficulty in obtaining the proper shape during fabrication. The present disclosures assures that the diamond or PDC material fully covers the end face or crown of the device. This is accomplished by constructing the diamond or PDC body initially with a facing shoulder of substantial width. Moreover, the shoulder is formed of soft, readily machinable, sacrificial material in the fabrication process so that it can be machined away easily. The excessive material is removed after the insert has been fabricated and the diamond or PDC layer has been placed on the end face.
Advantages which flow from this type of construction will become more readily understood upon description of the preferred embodiments of the insert and the methods of manufacture. Moreover, it is assumed that the inserts will be used in a body forming a drill bit which can be used in the most difficult of drilling situations. The inserts may be used in other abusive wear applications such as mining pick tips, bearings, metal cutting tools, etc.